Universal mobile telecommunications system (UMTS) is a 3rd generation (3G) asynchronous mobile communication system operating in wideband code division multiple access (WCDMA) based on European systems, global system for mobile communications (GSM) and general packet radio services (GPRS). The long-term evolution (LTE) of UMTS is under discussion by the 3rd generation partnership project (3GPP) that standardized UMTS.
Relaying is a technology that intermediates data between a user equipment (UE) and an eNodeB (eNB). 3GPP LTE-A (advanced) may support relaying by having a relay node (RN) wirelessly connect to an eNB serving the RN via an evolved universal terrestrial radio access (E-UTRA) radio interface. It may be referred to a section 4.7 of 3rd generation partnership project (3GPP) TS 36.300 V10.2.0 (2010-12). A relay node wirelessly communicates with an eNB supporting relay, and thus can support capacity assistance of a shadow region or coverage extension through a service for UEs located in a cell boundary region and outside the boundary region. The eNB serving the RN may be referred as a donor eNB (DeNB). The DeNB requires several additional functions for supporting relay. When there is an access of the relay node, the DeNB can perform a reconfiguration task to provide information required for relay and system information through dedicated signaling.
The RN may support eNB functionality so that the RN can be used for coverage improvement, supporting high data rate, and so on. It means that the RN terminates the radio protocols of the E-UTRA radio interface, and S1 and X2 interfaces. In addition to the eNB functionality, the RN may also support a subset of UE functionality, e.g., a physical layer, layer-2, radio resource control (RRC), and non-access stratum (NAS) functionality, in order to wirelessly connect to the DeNB. That is, the relay node can operate as a relay-type UE with respect to the DeNB, and can operate as an eNB with respect to a served UE.
The RN has two interfaces which are Un interface and Uu interface. The Un interface is a link between the eNB and the RN and the Uu interface is a link between the RN and the UE. The Un interface is a modified version of the E-UTRA radio interface. Depending on a type of the RN, whether an RN subframe configuration is required may be determined. The RN subframe refers to a downlink subframe allocated for the communication between the DeNB and the RN. If the RN subframe is necessary for the relay operation, the relay may request to the DeNB during an RRC connection setup procedure.
The RN may be classified to a fixed relay node and a mobile relay node (MRN). Recently, the MRN is considered as one of the issues in relay area. There is an increasing desire to use mobile broadband on public transportation especially on high speed trains. Providing high quality of service in fast moving environments is challenging due to challenging radio conditions as well as high and bursty signaling load. For addressing these issues, the MRN is raised as one of the solutions.
As the MRN moves, a location of a cell served by the MRN also may be changed. In this case, a physical cell identity (PCI) of the MRN cell served by the MRN may collide with a PCI of a neighbor cell.
Accordingly, a method of preventing the PCI of the MRN cell from colliding with the PCI of the neighbor cell is required.